GoKawiilAnte has taken the first step towards something we all thought was impossible: blending reference counting and borrow checking without run-time crashes. 0
This is very promising, because it means that someday, we can more easily use each approach when it makes sense without risking crashes. If there was a language like that, I could prototype a game in a flexible way with reference-counting, and gradually migrate it to faster borrow-checked code. 1
No mainstream language has figured out how to combine them seamlessly, even though many have tried.
Rust tried, but when we try to use Rust's reference-counting Rc type, it often requires RefCell (like Rc<RefCell<Spaceship>>) which can crash at run-time if you hold it wrong. 2 3 I wish rustc could check for proper Rc usage at compile-time! 4 5
Swift too has tried, with its new borrowing system, but it has an expensive run-time check which crashes at run-time if you hold it wrong.
It turns out, blending reference counting and borrow checking is hard, for reasons you'll see below.